The present invention relates to a fuel supply system of an internal combustion engine.
German Patent No. 41 31 952 describes a fuel supply system that has a fuel rail with a plurality of valve seats for injectors. The fuel rail, in this context, has a tubular base body, in whose interior a further tubular body is mounted. The fuel rail also contains a pressure regulator for maintaining a constant pressure in the fuel supply line of the tubular base body. The interior tubular body is made of elastically malleable material, so that it permits a modification of volume and/or form of the fuel supply line, if the pressure in it suddenly changes. The pressure regulator, in this context, is arranged on the fuel rail such that it is located downstream of the fuel supply line. To this extent, the interior tubular body, arranged for its part downstream of the pressure regulator, represents a return line. Therefore, the fuel supply system is operated in a manner such that fuel is supplied under pressure via a fuel connector to the fuel supply line in the outer tubular base body, from where it can reach the injectors. If the pressure in the fuel supply line exceeds a predetermined value, it acts upon the pressure regulator, in which a blocking element opens, as a result fuel flows into the interior tubular body functioning as a return line. The interior tubular body in principle only has fuel flowing through it if the fuel regulator has opened. Therefore, a design of this type is not suitable for fuel supply systems that do not have a return line.
German Patent No. 34 32 727 describes fuel supply lines for fuel injection systems of internal combustion engines. These fuel supply lines have one rigid wall part and at least one elastic wall part, connected to the former, so that the fuel pressure fluctuations, arising in response to the process of injecting fuel into the combustion chamber, are damped in the fuel supply line. The elastic wall part has considerable areas that must be outwardly sealed. This represents a safety risk for the operation of the internal combustion engine and for the environment. In addition, the elastic wall must be designed so as to be sufficiently rigid and fixed so that a tight seal for the system can be assured, which is achieved at the expense of the desired damping effect.
German Patent No. 43 41 368 describes a damper element for damping pressure fluctuations in the fuel supply system of an internal combustion engine. The system provides a damper element located in the fuel rail. The damper element is composed of one or more gas-filled chambers, whose walls are made of an elastic material. These chambers are arranged in the vicinity of the injectors, so as to achieve, in the process, the greatest damping effect on the pressure fluctuations originating from the injectors. In order to prevent clogging of the injectors, spacers must additionally be provided to assure, at every time point, a predetermined distance of the chambers from the valve seat feed pipes. However, in spite of the saving of space due to the damper element being housed in the fuel rail, this arrangement is expensive.
To operate fuel rail systems, it is usually necessary to use pressure regulators that reduce a higher intake pressure to a lower system pressure prevailing in the fuel rail. The design of pressure reducers of this type is conventional. Pressure reducers, in particular in fuel supply systems not having a return line, are arranged upstream and outside of the fuel rail. The control diaphragm is arranged on the system-pressure side and, at the same time, takes on a damping function. Thus, U.S. Pat. No. 5,398,655 describes a fuel regulating device for a fuel rail system that does not have a return line. The device has a pressure reducing valve arranged so as to be separate from the fuel rail. The valve either opens or closes as a function of the demand for fuel in the fuel rail system and, in this context, maintains an essentially constant pressure potential for the injectors. However, due to the additional devices, this system represents a safety risk, since, in response to damage that can occur, for example, in accidents, additional shortcomings in the tightness of the seal can arise.
For systems having return lines, conventional pressure regulating valves are used, usually arranged outside of the fuel rail tube. In these pressure-limiting valves, the diaphragm is positioned on the intake side. Since the return lines used are arranged in the fuel rail tube and are metallic and rigid, separate pressure dampers must be used in the return line, to avoid negatively impacting the system as a result of the pressure fluctuations arising therein.
A fuel supply system according to the present invention has the advantage that a damper element is arranged in the fuel rail itself, which makes possible, in particular, a simple design having the low associated manufacturing costs. On the basis of the arrangement according to the present invention, no further space is needed in the internal combustion engine or in the engine compartment. Further, the damping of the pressure fluctuations in the fuel supply of the rail system, brought about by the switching pulses of the injectors, is in the immediate vicinity of the point origin, i.e., of each injector, it being possible to avoid a reciprocal influencing of the quantity of fuel to be injected. Since the damper element is arranged internally, i.e., in the fuel rail itself, no additional seals need to be provided to the outside, thus reducing the danger of damage and the endangerment of the environment that is associated therewith.
In addition, the arrangement of the damper element, according to the present invention, is advantageous because it is positioned close to all existing injectors, and it can effectively counteract the fluctuations at their point of origin without, in the process, bringing about the danger of the damper element clogging the injectors. The arrangement of specific spacers is not required.
According to the present invention the pressure regulator, usually a pressure reducing valve is configured, so as to be integrated in the fuel rail. As a result, a simple, elastic tubular body, for example, a rubber tubing that is resistant to organic solvents, can be used as the damper element. The tubular body, arranged in the rail tube, permanently damps the fluctuations on the intake side. As a result of the arrangement of the damper element in the fuel rail itself, for example coaxially in regard to it, there is no direct contact of the damper element with the ambient environment, so that the danger of an outflow of fuel into the ambient environment is reduced.
A further advantage of this arrangement can be seen in the fact that the elastic tubular body arranged in the fuel rail not only permanently damps the fluctuations brought about by the operation of the injectors on the system side, i.e., in the fuel chamber of the rail that is external with regard to the tubular body, but the tubular body, on the intake side, can also take on damping functions with regard to pressure fluctuations brought about by the fuel-supply pump, because the inflow into the rail proceeds via the inner fuel chamber of the tubular body.